The Detroit Free Press, citing unnamed sources, said the SEC is requesting as many as one million pages of records on more than 150 investments.
Word of the expanding probe follows Free Press reports that the funds lost $480 million in risky investments since 2008.
The FBI and a federal grand jury have been investigating the pension funds and some failed deals, the newspaper said.
Over the past two years, staff members, current and former trustees and advisers have been subpoenaed to testify before the grand jury.
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